Add CN neural system

src/cognition-and-neuroscience/cn.tex

@@ -8,6 +8,8 @@
 \DeclareAcronym{epsp}{short=EPSP, long=excitatory postsynaptic potential, long-plural=s}
 \DeclareAcronym{ipsp}{short=IPSP, long=inhibitory postsynaptic potential, long-plural=s}
 \DeclareAcronym{ap}{short=AP, long=action potential, long-plural=s}
+\DeclareAcronym{cns}{short=CNS, long=central nervous system}
+\DeclareAcronym{pns}{short=PNS, long=peripheral nervous system}
 
 
 \begin{document}

src/cognition-and-neuroscience/sections/_nervous_system.tex

@@ -316,4 +316,458 @@ In a neuron, there are four regions that handle signals:
 
 \begin{example}
     Seizures are caused by misfiring neurons.
-\end{example}
+\end{example}
+
+
+
+\section{Information transfer between two neurons}
+
+
+\subsection{Electrical synapse}
+
+\begin{minipage}{0.55\textwidth}
+    \begin{description}
+        \item[Structure] \marginnote{Electrical synapse}
+            The neuronal membranes of the presynaptic and postsynaptic neurons are in contact at \textbf{gap junctions} and
+            the cytoplasm of the two neurons is virtually continuous through connecting \textbf{pores}.
+    \end{description}
+\end{minipage}
+\begin{minipage}{0.35\textwidth}
+    \centering
+    \includegraphics[width=\linewidth]{./img/electric_synapse.png}
+\end{minipage}
+
+\begin{description}
+    \item[Functioning]
+        The two neurons are \textbf{isopotential} (i.e. they have the same membrane potential) and 
+        the ions of the presynaptic neurons are instantaneously transmitted to the postsynaptic neuron.
+
+    \item[Properties] \phantom{}
+        \begin{itemize}
+            \item Fast transmission.
+            \item Allows for synchronous operations involving groups of neurons.
+            \item The strength of the signal cannot be modulated.
+        \end{itemize}
+\end{description}
+
+
+\subsection{Chemical synapse}
+
+\begin{description}
+    \item[Structure] \marginnote{Chemical synapse}
+        The synaptic cleft separates the presynaptic and postsynaptic neurons.
+        \begin{description}
+            \item[Neurotransmitter] 
+                Chemical substance received by the receptors of the postsynaptic neuron.
+
+                The effect of a neurotransmitter is decided by the receiving receptor and not by the cell transmitting it.
+
+            \item[Presynaptic terminals] 
+                Swellings at the end of the axon that contain synaptic vesicles.
+
+            \item[Synaptic vesicles] 
+                Vesicles containing neurotransmitter molecules.
+        \end{description}
+
+    \item[Functioning] 
+        The release of neurotransmitter molecules is based on the following steps:
+        \begin{enumerate}
+            \item An action potential arriving at the terminal of a presynaptic axon causes the calcium ion (Ca$^{2+}$) voltage-gates to open.
+            \item Ca$^{2+}$ flow into the cell and 
+                cause the synaptic vesicles to bind to the cell membrane to release neurotransmitters into the synaptic cleft.
+            \item Neurotransmitters cross the synaptic cleft and bind to the receptors of the postsynaptic neuron.
+                Depending on the neurotransmitter and the receiving receptor, there might be a generation of \ac{epsp} or \ac{ipsp}.
+        \end{enumerate}
+
+        \begin{center}
+            \includegraphics[width=0.9\linewidth]{./img/chemical_synapse.png}
+        \end{center}
+
+        When a receptor recognizes the neurotransmitter, it is released back into the synaptic cleft.
+        To avoid a constant stimulation of the receptors, neurotransmitters are inactivated:
+        \begin{itemize}
+            \item The synaptic terminal can reuptake neurotransmitters through transporter proteins.
+            \item Neurotransmitters might degenerate or be broken down by special enzymes.
+            \item Neurotransmitters can be released far away from the site of the receptors.
+        \end{itemize}
+
+    \item[Properties] \phantom{}
+        \begin{itemize}
+            \item Slow transmission.
+            \item The signal can be modulated.
+            \item Has specific effects depending on the neurotransmitter and the receptors.
+        \end{itemize}
+\end{description}
+
+
+
+\section{Neural circuit}
+
+\begin{description}
+    \item[Neural circuit] \marginnote{Neural circuit}
+        Group of interconnected neurons that process a specific kind of information.
+
+        \begin{remark}
+            The behavioral function of each neuron is determined by its connections.
+        \end{remark}
+
+    \item[Types of neurons] \phantom{}
+        \begin{description}
+            \item[Sensory neuron] \marginnote{Sensory neuron}
+                Carry information from the peripheral sensors to the nervous system for both perception and motor coordination.
+        
+            \item[Motor neuron] \marginnote{Motor neuron}
+                Carry information from the nervous system to muscles and glands.
+            
+            \item[Interneuron] \marginnote{Interneuron}
+                Intermediate neurons between sensory and motor neurons.
+        \end{description}
+\end{description}
+
+\begin{remark}
+    In vertebrates, a stimulus causes multiple neural pathways to simultaneously encode different information.
+    This allows for parallel processing to increase both the speed and reliability of the information transfer.
+\end{remark}
+
+\begin{description}
+    \item[Neural pathways types] \phantom{}
+        \begin{description}
+            \item[Divergent pathway] \marginnote{Divergent pathway}
+                One neuron activates many target cells.
+                Typically happens at the input stages of the nervous system
+                to ensure that a single neuron has a wide and diverse influence.
+
+            \item[Convergent pathway] \marginnote{Convergent pathway}
+                Many neurons activate a single target cell.
+                Typically happens at the output stages of the nervous system 
+                to ensure that a motor neuron is activated only when a sufficient number of neurons are firing.
+        \end{description}
+
+    \item[Neuron firing types] \phantom{}
+        \begin{description}
+            \item[Excitatory neuron] \marginnote{Excitatory neuron}
+                Neurons that produce signals that increase the probability of firing of the postsynaptic neurons.
+                
+            \item[Inhibitory neuron] \marginnote{Inhibitory neuron}
+                Neurons that produce signals that decrease the probability of firing of the postsynaptic neurons.
+                
+                \begin{description}
+                    \item[Feed-forward inhibition] 
+                        Excitatory neurons connected to inhibitory interneurons to block other downstream neurons.
+                        Allows to enhance the active pathway and to block other antagonist actions.
+                        \begin{figure}[H]
+                            \centering
+                            \includegraphics[width=0.4\textwidth]{./img/feedforward_inhibition.png}
+                            \caption{Example of feed-forward inhibition}
+                        \end{figure}
+
+                    \item[Feed-back inhibition] 
+                        Excitatory neurons connected to inhibitory interneurons that return to the same neurons to inhibit them.
+                        Prevents the overload of neurons or muscles.
+                        \begin{figure}[H]
+                            \centering
+                            \includegraphics[width=0.4\textwidth]{./img/feedback_inhibition.png}
+                            \caption{Example of feed-back inhibition}
+                        \end{figure}
+                \end{description}
+        \end{description}
+\end{description}
+
+
+
+\begin{example}[Knee-jerk reflex]
+    By tapping the patellar tendon (below the kneecap), the following happens:
+    \begin{enumerate}
+        \item The sensory information is conveyed from the muscle to the spinal cord (central nervous system).
+        \item The nervous system issues motor commands to the muscles which results in the knee jerk.
+        \item Inhibitory commands are issued to stop antagonist muscles.
+    \end{enumerate}
+
+    \begin{center}
+        \includegraphics[width=0.8\textwidth]{./img/knee_jerk.png}
+    \end{center}
+\end{example}
+
+
+\section{Neural system}
+
+\begin{figure}[H]
+    \centering
+    \includegraphics[width=0.3\textwidth]{./img/neural_system.png}
+    \caption{Composition of the nervous system}
+\end{figure}
+
+
+\subsection{\Acl{pns} (\acs{pns})}
+
+The \acl{pns} is composed of:
+\begin{descriptionlist}
+    \item[Nerves] \marginnote{Nerves}
+        Groups of axons and glia.
+
+    \item[Ganglia] \marginnote{Ganglia}
+        Groups of neuron bodies outside the \acl{cns}
+\end{descriptionlist}
+
+The \ac{pns} has the following functions:
+\begin{itemize}
+    \item Delivers sensory information to the \acl{cns}.
+    \item Carries commands from the \acl{cns} to the muscles.
+    \item Supplies the \acl{cns} with information regarding both the external and internal environment.
+\end{itemize}
+
+The \ac{pns} has the following divisions:
+\begin{descriptionlist}
+    \item[Somatic nervous system] \marginnote{Somatic nervous system} \phantom{}
+        \begin{itemize}
+            \item Sensory neurons that receive information from the skin, muscles, and joints.
+            \item Converts perceived spatial and physical information into electrical signals for the \acl{cns} to process.
+            \item Controls the voluntary muscles.
+        \end{itemize}
+
+    \item[Autonomic nervous system] \marginnote{Autonomic nervous system} \phantom{}
+        \begin{itemize}
+            \item Controls internal organs (viscera), the vascular system, and involuntary muscles and glands.
+            \item Divided into three systems:
+                \begin{descriptionlist}
+                    \item[Sympathetic system] \marginnote{Sympathetic system}
+                        Operates antagonistically against the parasympathetic system.
+                        Handles the body's response to stress (using norepinephrine).
+
+                        Physically, the sympathetic system originates from the spinal cord. 
+                        Its ganglia are closer to the spinal cord,
+                        therefore the axons from the \acl{cns} to the ganglia are shorter than the axons from the ganglia to the organs.
+
+                        \begin{example}
+                            Stimulates adrenal glands to prepare the body for action (fight or flight),
+                            increases heart rate,
+                            diverts the blood from the digestive tract to the somatic musculature, \dots
+                        \end{example}
+
+                    \item[Parasympathetic system] \marginnote{Parasympathetic system}
+                        Operates antagonistically against the sympathetic system.
+                        Acts to preserve the body's resources and restore homeostasis (using acetylcholine).
+
+                        Physically, the parasympathetic system originates from the base of the brain and from the sacral spinal cord.
+                        Its ganglia are outside the spinal cord, sometimes inside the affected organs,
+                        therefore the axons from the \acl{cns} to the ganglia are longer than the axons from the ganglia to the organs.
+
+                        \begin{example}
+                            Slows heart rate, stimulates digestion, \dots
+                        \end{example}
+
+                    \item[Enteric system] \marginnote{Enteric system}
+                        Controls the involuntary muscles of the gut.
+                \end{descriptionlist}
+        \end{itemize}
+\end{descriptionlist}
+
+
+
+\subsection{\Acl{cns} (\acs{cns})}
+
+\begin{description}
+    \item[Meninges] \marginnote{Meninges}
+        Three layers of membrane protecting the brain and the spinal cord.
+        \begin{descriptionlist}
+            \item[Dura mater] The outermost and thickest layer.
+            \item[Arachnoid mater] The middle layer.
+            \item[Pia mater] The innermost and most delicate layer. It adheres to the brain's surface.
+        \end{descriptionlist}
+
+    \item[Cerebrospinal fluid] \marginnote{Cerebrospinal fluid}
+        Fluid that allows the brain to float and prevents it from simply sitting on the skull surface.
+        It also reduces the shock to the brain and the spinal cord in case of rapid accelerations/decelerations.
+
+        The fluid is located in:
+        \begin{itemize}
+            \item The space between the arachnoid mater and the pia mater.
+            \item The brain ventricles.
+            \item Cisterns and sulcis.
+            \item The central canal of the spinal cord.
+        \end{itemize}
+
+    \item[Blood-brain barrier] \marginnote{Blood-brain barrier}
+        Barrier between the brain's capillaries and the brain's tissue.
+        It protects against pathogens and toxins.
+
+        \begin{remark}
+            The effectiveness of the barrier also prevents drugs to treat mental and neurological disorders from passing through.
+        \end{remark}
+
+    \item[Spinal cord] \marginnote{Spinal cord}
+        Acts as a relay for the information coming in and out of the brain.
+        It is enclosed in the vertebral column.
+\end{description}
+
+\begin{remark}
+    Most pathways in the \ac{cns} are bilaterally symmetrical: 
+    the sensory and motor activities of one side of the body are handled by the cerebral hemisphere on the opposite side.
+\end{remark}
+
+\begin{description}
+    \item[Brain] \marginnote{Brain}
+    
+    \begin{minipage}{0.6\textwidth}
+        \begin{description}
+            \item[Brain stem] \marginnote{Brain stem}
+                Regulates basic life functions such as blood pressure, respiration, and sleep/wakefulness.
+                It is divided into three sections:
+                \begin{itemize}
+                    \item Medulla.
+                    \item Pons.
+                    \item Midbrain.
+                \end{itemize}
+        \end{description}
+    \end{minipage}
+    \begin{minipage}{0.35\textwidth}
+        \centering
+        \includegraphics[width=\linewidth]{./img/brain_sections.png}
+    \end{minipage}
+
+    \begin{description}
+        \item[Cerebellum] \marginnote{Cerebellum}
+            Contains lots of neurons and is responsible for:
+            \begin{itemize}
+                \item Maintaining posture.
+                \item Coordinating head, eye, and arm movement.
+                \item Regulating motor control (i.e. adjustments to the movement).
+                \item Learning motor skills.
+            \end{itemize}
+
+        \item[Diencephalon] \marginnote{Diencephalon} 
+            \phantom{}\\
+            \begin{minipage}{0.6\linewidth}
+                \begin{description}
+                    \item[Thalamus] \marginnote{Thalamus}
+                        Sorts incoming sensory information (except the sense of smell) of the \acl{pns} and 
+                        sends them to the sensory regions of the cerebral hemispheres.
+                    \item[Hypothalamus] \marginnote{Hypothalamus}
+                        Regulates the autonomic nervous system and homeostasis through the pituitary gland (which releases hormones).
+                        Handles the motivation system of the brain by favoring behaviors the organism finds rewarding.
+                \end{description}
+            \end{minipage}
+            \begin{minipage}{0.35\linewidth}
+                \centering
+                \includegraphics[width=\linewidth]{./img/diencephalon.png}
+            \end{minipage}
+
+        \item[Telencephalon/Cerebral hemispheres] \marginnote{Telencephalon/Cerebral hemispheres}
+            Consists of:
+            \begin{description}
+                \item[Cerebral cortex] 
+                    Made of gray matter (body of neurons).
+
+                \item[White matter] 
+                    (axons and glial cells).
+
+                \item[Basal ganglia] \marginnote{Basal ganglia}
+                    Receive inputs from sensory and motor areas and 
+                    mostly send them through the thalamus to the frontal lobe.
+
+                    They have a crucial role in motor control and reinforcement learning.
+                    This happens through two pathways:
+                    \begin{description}
+                        \item[Direct pathway] When active, it causes the disinhibition of the thalamus and has the consequence of initializing movement.
+                        \item[Indirect pathway] When active, it causes the inhibition of the thalamus and consequently inhibits movement.
+                    \end{description}
+                    To activate the direct pathway and inhibit the indirect pathway, the substantia nigra pars compacta (SNc) releases the neurotransmitter dopamine.
+
+                    \begin{example}[Parkinson's disease]
+                        In patients affected by Parkinson's disease, the dopamine-related neurons in the SNc are lost causing
+                        an overactivation of the indirect pathway that inhibits movement.
+                    \end{example}
+
+                \item[Amygdala] \marginnote{Amygdala}
+                    Responsible for recognizing a stimulus and reacting to it.
+                    Involved in attention, perception, value representation, decision-making, learning, memory, \dots
+
+                \item[Hippocampus] \marginnote{Hippocampus}
+                    Responsible for long-term memory and spatial memory.
+            \end{description}
+
+        \item[Cerebral cortex] \marginnote{Cerebral cortex}
+            Surface of the brain which covers around 2.2m$^2$ to 2.4m$^2$.
+            To cover more surface, the cortex has infoldings (sulci and gyri) which also allow to connect neurons with shorter axons.
+
+            There are two symmetrical hemispheres connected through the corpus callosum and four different lobes.
+
+            \begin{figure}[H]
+                \centering
+                \begin{subfigure}{0.25\linewidth}
+                    \centering
+                    \includegraphics[width=\linewidth]{./img/brain_surface.png}
+                    \caption{Visualization of sulci and gyri}
+                \end{subfigure}
+                \begin{subfigure}{0.35\linewidth}
+                    \centering
+                    \includegraphics[width=\linewidth]{./img/brain_lobes.png}
+                    \caption{Lobes of the brain}
+                \end{subfigure}
+            \end{figure}
+
+            \begin{description}
+                \item[Frontal lobe] \marginnote{Frontal lobe}
+                    \phantom{}
+                    \begin{description}
+                        \item[Motor cortex] \phantom{}
+                            \begin{itemize}
+                                \item Planning and execution of movement.
+                                \item Contains neurons that directly activate somatic movement neurons in the spinal cord.
+                            \end{itemize}
+
+                        \item[Prefrontal cortex] \phantom{}
+                            \begin{itemize}
+                                \item Long-term planning.
+                                \item Decision making.
+                                \item Motivation and value.
+                            \end{itemize}
+                    \end{description}
+                
+
+                \item[Parietal lobe] \marginnote{Parietal lobe}
+                    Receives and integrates information from the outside world, the body, and memory.
+
+                    \begin{description}
+                        \item[Somatosensory cortex]
+                            Receives information regarding touch, pain, temperature, and limb position.
+                    \end{description}
+
+                    \begin{remark}
+                        Neurons responsible for a specific part of the body are clustered together.
+                    \end{remark}
+
+
+                \item[Occipital lobe] \marginnote{Occipital lobe}
+                    \begin{description}
+                        \item[Visual cortex] 
+                            Responsible for vision. 
+                            Encodes features like luminance, spatial frequency, orientation, motion, \dots
+                    \end{description}
+
+                    \begin{remark}
+                        Neurons responsible for processing a specific feature are clustered together.
+                    \end{remark}
+
+
+                \item[Temporal lobe] \marginnote{Temporal lobe}
+                    \begin{description}
+                        \item[Auditory cortex]
+                            Responsible for processing sound.
+                    \end{description}
+
+                    \begin{remark}
+                        Neurons responsible for processing a specific sound frequency are clustered together.
+                    \end{remark}
+
+                \item[Association cortex] \marginnote{Association cortex}
+                    Portion of the cortex that has neither sensory nor motor responsibility.
+                    Receives and integrates inputs from many cortical areas.
+
+                    \begin{description}
+                        \item[Multisensory neuron]
+                            Cell activated by multiple sensory modalities.
+                    \end{description}
+            \end{description}
+    \end{description}
+\end{description}